Next, as in [1]}, we consider a local Cartesian coordinate frame
\(\left( x,y,z\right) \)  comoving with the apparatus with small size compared
to the scale on which the metric varies. This approximation is carefully
justified in [2]}. Hence we have the following line element, where all
metric components are taken as constants,
\(ds^{2}=g_{tt}dt^{2}+2g_{tx}dtdx+g_{xx}dx^{2}+g_{yy}dy^{2}+g_{zz}dz^{2}~,\) 
